Treatment of fibrous material



Patented Oct. 26, 1954 TREATMENT OF FIBROUS MATERIAL John Bamber Speakman and Alan Crummett,

Leeds, England, assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application March 4, 1947, Serial No. 732,384

Claims priority, application Great Britain March 12, 1946 6 Claims. 1

This invention relates to the production of felts and especially to the production of felts from a mixture of wool fibres (or other animal fibres capable of felting) with fibres of cellulose acetate or other cellulose ester or ether, in which mixture the fibres are disposed at random.

A felt is readily produced from a mass of randomly disposed wool fibres by subjecting it to suitable mechanical squeezing and rolling treatment while moist. Such mechanical treatments are hereinafter referred to as felting treatments. on a manufacturing scale, machines are employed which subject the mass of moist wool to repeated application and release of pressure such as can be secured by passing the mass of material repeatedly between pairs of rollers adapted to squeeze the material. One form of roller felt making machine comprises a horizontal set of parallel, closely spaced but non-contacting rollers, alternate rollers being steam-heated and all the rollers being driven. A second set of freely rotatable rollers rests on the first mentioned set so that each roller of the upper set makes contact with two rollers of the lower set. The upper rollers are often given an oscillatory movement in the direction of their axes. The material to be given a felting treatment is passed, usually on a canvas belt, between the two sets of rollers in a direction at right angles to their axes. The material can then pass through twice as many nips as there are upper rollers. Means are usually provided for supplying moisture to the material undergoing felting; thus the canvas belt can be endless and arranged to pass through a water trough just before it enters the roller system. In another form of felt making ma chine the material is subjected to intermittent pressure between two plate-like members as the material passes continuously between them; one of the members may simultaneously be given an oscillatory movement in its own plane. Treatment in such machines whether of the roller or plate type is of the kind often referred to as felt hardening. After a coherent product has been obtained by such a process, it is often subjected to a milling treatment of the kind commonly applied to woollen textile fabrics made from yarns, whereby further felting and compacting of material can be effected. Felts can be produced by similar means from other felting fibres, for example from fur fibres which have been carrotted.

Cellulose acetate fibres, in common with many other natural and artifical fibres, particularly cellulose fibres, show very little tendency to felt.

, or ether fibre is in a softened condition. Not

only is felting more readily effected, but products can be obtained which are more compact than can be obtained when the felting is attempted without first softening the cellulose ester or ether fibres.

According to the present invention the felting of a mixture of wool, or other animal fibres which felt, with staple fibres of cellulose acetate or other cellulose ester or ether is effected by subjecting the mixture to a felting treatment while the cellulose acetate or other cellulose ester or ether fibres is in a softened condition.

The softening of the cellulose acetate or other cellulose ester or ether fibres can be effected most conveniently with the aid of organic soften ing agents therefore. The agent employed can be such as to shrink the cellulose ester or ether fibre, but should not, of course, be such as to destroy the fibre form. Single organic substances can be used, but usually it is convenient to employ mixtures of organic substances, or, better still, mixtures of organic substances with water. Mixtures have the advantage that, by adjusting the proportions of the constituents, the

; softening power can be adjusted within wide limits. In the case of cellulose acetate fibres, mixtures of water with water-miscible solvents for cellulose acetate have been found very useful: for example, mixtures of water with diacetone alcohol, acetone, ethylene-methylene ether, dioxane, ethyl acetate, phenol or a cresol, or a lower aliphatic acid e. g. formic acid, acetic acid, propionic acid or other lower fatty acid, or monochloracetic acid, glycollic acid, lactic acid or other halogen or hydroxy derivative of a lower fatty acid, especially an alpha derivative. Very good results can be obtained by using aqueous acetic acid 30-50% strength by volume and particularly by using acid of about 40% strength at ordinary temperatures. Again, diacetone alco- 1101, of 50-65% strengthparticularly about 60% strength-can be employed at 20-25 C., or other softening agents of such nature and at such temperature that they have a softening effect on the cellulose acetate similar to that of the aqueous acetic acids or aqueous diacetone alcohols mentioned. Thus, aqueous glycol monomethyl ether acetate of about 40% strength at -25" C. can be used.

Lower fatty acids, particularly acetic acid and formic acid have been found to yield particularly good results when employed, at ordinary temperatures of say 15 to C., as aqueous solutions of strengths of the order of those indicated above.

In the case of acetic acid, concentrations of to strength and particularly about 40% strength (by volume) are to be recommended. In the case of formic acid the strength (by volume) is advantageously rather lower, for example 32 to 40% and particularly about 36%.

latter to felt more readily than is ordinarily the case when the animal fibres are moistened with water. Indeed, moistening with aqueous acetic or formic acid effects a note-worthy acceleration of the rate of felting of a mass consisting entirely of wool fibres or other animal fibres capable of felting. We include within the scope of our invention this method of accelerating the felting of masses of wool or other animal fibres capable of felting.

If desired, the organic softening agents can be wholly or in part replaced by inorganic softening agents for the cellulose ester or ether: for example, ammonium, alkali metal or alkaline earth metal thiocyanates. Thus, an aqueous solution of one of these thiocyanates can be employed.

The felting treatment of the present invention is most advantageously applied to mixtures of cellulose ester or ether fibres with wool or other animal fibres containing at least by weight of the latter. Good felts can, for example, be produced from a mixture of wool fibres and cellulose acetate fibres containing from to 80% by weight of the former.

For the production of felt in sheet form the mixture of wool or the like with cellulose ester or ether fibres should be in the form of a sheet or batt. Such sheet material may be prepared by carding the wool and cellulose ester or ether fibres together on a carding machine which dea.

livers its product in the form of a sheet. The sheet or batt subjected to felting treatment may be composite sheet or batt made by superposing two or more sheets as delivered by the carding machine. In this way can be obtained sheets or batts which are of a high degree of uniformity as regards weight per unit area and in which the wool fibres and cellulose ester or ether fibres are very intimately mixed.

The application of the softening liquid to the mixture of fibres is conveniently effected by soaking the mass of fibre in the softening liquid for a sufficient time to ensure thorough wetting, for example, for half to one hour. The material may thereafter be squeezed, hydroextracted or otherwise treated so as to reduce the amount of liquid retained by the material to about 100%, based on the weight of the material. In the case of preparing the felt in sheet form, a batt of the mixture of fibres may first be prepared, passed iii) through the softening liquid, squeezed to reduce the content of softening liquid to the requisite degree, and the moistened batt thereafter subjected to the felting treatment.

The invention is not restricted to the application of the softening liquid to the material before any felting operation has been performed: for example, the mixture of fibres may be assembled in the form of a batt, the latter subjected to a hardening treatment and the hardened prod uct moistened with the softening liquid and thereafter subjected to felting or further felting. The invention particularly contemplates a process wherein a batt of a mixture of wool (or other animal fibres which felt) with staple fibres of cellulose acetate or other cellulose ester or ether is subjected to a felting treatment in the absence of any organic softening agent for the cellulose ester or ether, for example while moistened with water, and is thereafter maintained with an organic softening agent for the cellulose ester or ether and subjected to further felting treatment.

The invention will now be described in greater detail with reference to the production of felt in sheet form from a mixture of wool fibres and cellulose acetate staple fibres.

'75 parts of wool and 25 parts of cellulose aoetate staple fibres are carded together on a carding machine, the product being delivered as a sheet. By superposing these sheets a batt is prepared having a weight of one to two pounds per square yard. The batt is then passed through a roller type felt hardening machine of the kind described above so as to obtain a coherent sheet. The latter is then moistened with aqueous acetic acid of about 40% strength by volume with the aid of a padding mangle, the rollers of the latter being adjusted so that the batt retains about its own weight of the aqueous acid. The batt is then given a further felting treatment either on a roller felt hardener of the kind referred to above or on a milling stock or roller type milling machine of the kind used for milling woven woollen fabrics. A firm well felted product can thus be obtained whereas if the aqueous acetic acid is replaced by water or a soap solution. as commonly used in the case of all-wool felts, the same degree offelting'and compacting cannot be obtained.

7 An all-woo1 felt may be prepared in a similar manner.

Felts produced in accordance with the process of the present invention may, if desired or necessary having regard to the character of material required, be subjected to a milling operation. of the kind such as is commonly applied to woven textile fabrics of wool.

The invention has been more particularly described in connection with the production of felts from wool or mixtures of wool with cellulose acetate fibres. In place of wool other animal fibres capable of felting may be employed, for example fur fibres which have been carrotted. Again the mixtures may comprise fibres of other cellulose ester or ethers, for example, cellulose 'propiona-te, cellulose butyrate, mixed esters, for example cellulose acetate-propionate or cellulose acetate-butyrate, ethyl cellulose and benzyl cellulose. Further, the cellulose acetate or other cellulose ester or ether fibres may be such as are obtained directly by dry spinning processes, or

they may be such as are obtained by dry spinning processes followed by stretching in the presence of a softening agent, for example, hot water or wet steam.

Accordin to a modification of the invention, the cellulose ester or ether fibres are replaced wholly or in part by fibres of other organic fibreforming material soluble in organic liquids. Examples of such fibres are those of polymerised vinylidene chloride, or of a copolymer of vinyl chloride with vinyl acetate or fibres of linear superpolyamides, for example, nylon.

Having described our invention, what We desire to secure by Letters Patent is:

1. A process for the production of felt from a random mixture of animal fibers, capable of felting, and cellulose acetate staple fibers, which comprises subjecting said random mixture in the form of a sheet to intermittent pressure between solid surfaces oscillating in a plane parallel to said sheet while said sheet is in contact with a liquid, the amount of said liquid being about equal to the weight of said sheet, said liquid being a mixture comprising water and a lower aliphatic acid and having substantially the same softening action on cellulose acetate as has aqueous acetic acid of 30 to 50% strength by volume at 15 to 25 C.

2. A process for the production of felt from a random mixture of wool fibers and cellulose acetate staple fibers, which comprises subjecting said random mixture in the form of a sheet to intermittent pressure between solid surfaces oscillating in a plane parallel to said sheet while said sheet is in contact with a liquid, the amount of said liquid being about equal to the weight of said sheet, said liquid being a mixture comprising water and a lower aliphatic acid and having substantially the same softening action on cellulose acetate as has aqueous acetic acid of 30 to 50% strength by volume at 15 to 25 C.

3. A process for the production of felt from a random mixture of wool fibers with cellulose acetate staple fibers, which comprises subjecting said random mixture in the form of a sheet to intermittent pressure between solid surfaces oscillating in a plane parallel to said sheet while said sheet is in contact with a liquid, the amount of said liquid being about equal to the weight of said sheet, said liquid being aqueous acetic acid of 30 to 50% strength by volume.

4. A process for the production of felt from a random mixture of wool fibers with cellulose acetate staple fibers, which comprises subjecting said random mixture in the form of a sheet to intermittent pressure between solid surfaces oscillating in a plane parallel to said sheet while acid of about 40% strength by volume.

5. A process for the production of felt from a j random mixture of wool fibers with cellulose acetate staple fibers, which comprises subjecting said random mixture in the form of a sheet to intermittent pressure between solid surfaces oscillating in a plane parallel to said sheet while said sheet is in contact with a liquid, the amount of said liquid being about equal to the weight of said sheet, said liquid being aqueous formic acid of 30 to 40% strength by volume.

6. A process for the production of felt, which comprises subjecting a sheet consisting of a random mixture of wool fibers and cellulose acetate staple fibers and containing -80% by weight of the former to a felt hardening operation to obtain a coherent sheet, then subjecting said coherent sheet to intermittent pressure between solid surfaces oscillating in a plane parallel to said sheet while said sheet is in contact with a liquid, the amount of said liquid being about equal to the weight of said sheet, said liquid being aqueous acetic acid of 30 to 50% strength by volume.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 248,536 Waring Oct. 18, 1881 2,123,934 Dicke et al. July 19, 1938 2,156,455 Kleine May 2, 1939 2,252,999 Wallach Aug. 19, 1941 2,270,223 Schlack Jan. 13, 1942 2,277,049 Reed Mar. 24, 1942 2,296,329 Bell et al Sept. 22, 1942 2,338,792 Whitehead Jan. 11, 1944 2,352,245 Bell June 27, 1944 2,357,392 Francis Sept. 5, 1944 2,407,602 Cluley Sept. 10, 1946 2,444,115 Reed June 29, 1948 2,464,301 Francis, Jr Mar. 15, 1949 2,483,406 Francis, Jr. Oct. 4, 1949 2,586,105 Speakman et al. Feb. 19, 1952 2,586,106 Speakman et al. Feb. 19, 1952 

1. A PROCESS FOR THE PRODUCTION OF FELT FROM A RANDOM MIXTURE OF ANIMAL FIBERS, CAPABLE OF FELTING, AND CELLULOSE ACETATE STAPLE FIBERS, WHICH COMPRISES SUBJECTING SAID RANDOM MIXTURE IN THE FORM OF SHEET TO INTERMITTENT PRESSURE BETWEEN SOLID SURFACE OSCILLATING IN A PLANE PARALLEL TO SAID SHEET WHILE SAID SHEET IS IN CONTACT WITH A LIQUID, THE AMOUNT OF SAID LIQUID BEING ABOUT EQUAL TO THE WEIGHT OF SAID SHEET, SAID LIQUID BEING A MIXTURE COMPRISING WATER AND A LOWER ALIPHATIC ACID AND HAVING SUBSTANTIALLY THE SAME SOFTENING ACTION ON CELLULOSE ACETATE AS HAS AQUEOUS ACETIC ACID OF 30 TO 50% STRENGTH BY VOLUME AT 15 TO 25* C. 